Known as construction machines employed in construction work, demolition work, civil engineering work and/or the like include those having an upperstructure mounted rotatably on an undercarriage and a multi-articulated front working mechanism attached pivotally up and down to the upperstructure. As one example of such working machines, there is a demolition work machine constructed by using a hydraulic excavator as a base.
Such a working machine includes a front working mechanism, which is composed of a boom and arm and is connected pivotally up and down to an upperstructure via a joint, and a grapple, bucket, breaker, crusher or the like attached to a free end of the arm via a joint, so that it can perform work such as demolition work of structural objects or dismantling work of waste.
Work by such a working machine is performed by variously changing its posture with a boom, arm and working attachment (which will be represented by a bucket), which make up a front working mechanism, being kept extending to an outside of the upperstructure. The working machine may, therefore, tip over if an unreasonably aggressive operation is performed.
As a conventional technology for this problem, Patent Document 1 may be referred to, for example. According to the technology disclosed in Patent Document 1, a working machine is provided at its boom and arm with angle sensors, respectively, a controller is arranged in the working machine, and detection signals from the angle sensors are inputted to the controller. The controller computes, based on the detection signals, a barycentric position of the entire working machine and bearing power at each steady supporting point in a ground contact area of an undercarriage, and based on the results of the computation, displays on a display the values of bearing power at the respective steady supporting points. The controller is also configured to produce a warning when the bearing power at a rear steady supporting point of the working machine has decreased to a threshold limit value for the assurance of safe work.
As another example, reference may also be had to Patent Document 2, for example. According to the technology disclosed in Patent Document 2, a working machine is provided with angle sensors for detecting its boom angle, arm angle and bucket angle and a swing angle of its upperstructure and also with a tilt angle sensor for detecting a longitudinal tilt of a body. Based on these angle sensors and the dimensions of predetermined parts of the body, the static tipping moment of the working machine is computed.
In addition, the dynamic tipping moment produced under a centrifugal force as a result of rotation of the upperstructure is also computed by using a rotational angular velocity of the upperstructure, and moreover, the dynamic tipping moment produced at the time of a sudden stop of the upperstructure is also computed by using the maximum angular acceleration of the rotation. Either one or greater one of these dynamic tipping moments is added to the static tipping moment, and its magnitude is employed as a condition for the determination of tipping. Under the determination condition so established, the rotational angular velocity is controlled.
As a further example, reference may be had to Patent Document 3, for example. The technology disclosed in Patent Document 3 includes sensors for detecting a posture and motion of a main body of a construction machine and a work load on the main body of the construction machine. With reference to data base, a model is built based on detection values of these sensors such that the model can represent current and future mechanical behaviors on the posture of the main body of the construction machine to determine whether or not the main body of the construction machine would tip over. When tipping is predicted, the working operation under performance is stopped, and moreover, an operation is initiated to avoid tipping, thereby making it possible to avoid tipping. This technology is also configured such that, when tipping is predicted, an operator is notified accordingly.